Radio-frequency signals are also generally called radio signals and by extension radio-frequency signal receivers are referred to as radio receivers.
In the description and the claims that follow the following terminology will be used.
An “analogue signal” is a signal that can vary continuously both over time and in amplitude.
A “digital signal” is a signal which takes discrete values, at regular intervals over time.
A “sampled signal” is a signal whose value changes at regular intervals over time.
A “continuous time signal” is a non-sampled signal, that is, a signal whose value can change at any time.
A “quantized signal” is a signal which can take discrete values over time at any instant.
A “binary signal” is a quantized signal which can take a maximum of two values. A quantized signal which can take more than two values may be transmitted in the form of several binary signals, each representing one bit of the quantized signal.
“Decimate” means to suppress a part of the samples of a sampled signal in order to sub-sample the latter.
A “cycle” of a binary signal is the portion of the signal which extends from a predetermined transition of the signal, for example the transition from its high value to its low value, up to the following predetermined transition. In the case of a periodic signal, therefore, a cycle corresponds to one period of the signal.
A “quantization device”, or “quantizer”, is a device which transforms a signal into a quantized signal, that is, which supplies a quantized signal whose value depends on the value of the analogue signal over time.
The “positive envelope”, hereafter referred to simply as “envelope”, of a signal is a curve of low frequency in relation to the main frequency which seeks to join the peaks (local maxima) of the signal together. In the case of a carrier which is only amplitude modulated, the envelope is the amplitude modulation. A signal which takes positive and negative values also exhibits a negative envelope which seeks to join the downwards peaks (local minima) of the signal together. In the case of a signal which is symmetrical around zero, the negative envelope is approximately equal to the opposite of the positive envelope.
An analogue-digital converter is often an essential element of electronic devices, in particular of radio receivers with a digital architecture where the radio signal emerging from the antenna has to be digitised.